This application claims the priority of Korean Patent Application No. 2002-40393 filed on Jul. 11, 2002 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a stack type heat exchanger used as an evaporator of an air conditioner for a car, and more particularly, to a stack type heat exchanger having an improved inner structure to enhance cooling performance.
2. Description of the Related Art
A heat exchanger exchanges heat by making two fluids having different temperatures directly or indirectly contact each other. The heat exchanger includes a path through which heat exchange medium flows. While the heat exchange medium flows in the path, heat exchange with outside air is performed. A variety of types of heat exchangers are provided in an air conditioning system of a car. For example, there is a heater core for heating a car, a radiator for cooling the engine of a car, a condenser and an evaporator for cooling a car, and an oil cooler for cooling oil for an automatic transmission.
Among the above heat exchangers, the heat exchanger for an evaporator has been developed in various ways according to the type of refrigerant used as a heat exchange medium and internal pressure generated in the heat exchanger. Typically, there is a fin tube type, a serpentine type, a drawn cup type, a parallel flow type, and a plate and fin type which is referred to as a stack type.
FIG. 1 is a perspective view illustrating a stack type heat exchanger disclosed in Japanese Utility Model Publication No. hei 7-12778 which is an example of a heat exchanger for an evaporator.
Referring to FIG. 1, a conventional stack type heat exchanger 10 is made by stacking a plurality of unit frames, each of which includes a pair of parallel flat tubes 22 formed by combining a pair of plates and through which refrigerant flows and a tank 31 disposed at each of upper and lower ends of the flat tubes 22. The stacked flat tubes 22 and radiation fins 24 interposed between the flat tubes 22 constitutes a heat exchange core portion 20. The tanks 31 are stacked to form first through fourth tank groups 41 through 44. However, although a third tank group is not shown in the drawing, the position thereof can be easily understood. The tanks in the different tank groups are not connected to each other. An inlet pipe 11 and an outlet pipe 12 are provided at the tank at an end of the first tank group 41 in a direction of +X axis and the tank at an end of the second tank group 42 in the same direction, respectively. A connection unit 51 is provided at the opposite ends of the first and second tank groups 41 and 42 in a direction of −X axis.
FIG. 2 is a perspective view illustrating the flow of refrigerant inside the heat exchanger of FIG. 1. Although constituent elements are not detailed in the drawing, they may be easily understood by referring to FIG. 1.
According to FIG. 2, refrigerant coming into the tank of the first tank group 41 through the inlet pipe 11 flows downward and upward along the flat tubes 22 by being blocked by a blocking plate 33 installed at a tank in a middle portion of the first tank group 41. The refrigerant flows toward the tank of the second tank group 42 through the connection unit 51. Then, the refrigerant flows downward and upward along the flat tubes 22 by being blocked by a blocking plate 34 installed at a tank in a middle portion of the second tank group 42, and is exhausted through the outlet pipe 12.
When the above flow of refrigerant is viewed in terms of the blocking plates 33 and 34, in a first flow I between the inlet pipe 11 and the blocking plate 33, the refrigerant concentrates around the inlet pipe 11 by being affected by the gravity. In a second flow II between the blocking plate 33 and the connection unit 51, the refrigerant concentrates around the connection unit 51 due to a inertia force. Similarly, in a third flow III between the connection unit 51 and the blocking plate 34, the refrigerant concentrates around the connection unit 51. In a fourth flow IV between the blocking plate 34 and the outlet pipe 12, the refrigerant concentrates around the outlet pipe 12.
As a result, the refrigerant may concentrate in peripheral portions of the heat exchange core portion 20. Thus, the temperature of air exhausted into the inside of a car is irregular and cooling performance of an air conditioner is deteriorated.
In the meantime, Japanese Patent Publication No. 2000-105091 discloses a stack type heat exchanger in which a protruding portion for determination of a stack position is formed on a combined surface of a tank to easily determine the stacking position of the tanks, equipments are automated by depressing a connection hole, and the amount of pressure drop in refrigerant can be reduced.
Further, Japanese Patent Publication No. hei 10-325645 discloses a stack type heat exchanger in which a bypass route having an area smaller than an area of a refrigerant path for evaporation is provided at least one position of a heat exchange unit to increase the amount of lubricate flowing in a compressor.
However, in these heat exchangers, since the heat exchanger is uniformly designed with respect to the direction of flow of refrigerant without considering the gravity and inertia at the respective portions of the heat exchanger, the irregular concentration of the refrigerant may occurs.